The use of an auxiliary combustion chamber device, often referred to as a prechamber device or a prechamber ignition device, in an engine to control ignition and improve fuel utilization or otherwise improve or affect performance is well known in the art. Prechamber devices generally include an auxiliary combustion chamber (i.e., a combustion prechamber or a prechamber) for combusting a mixture of air and fuel. Combustion in the prechamber is frequently spark-initiated by a sparkplug or the like. The resulting combustion gases expand rapidly, eventually escaping the prechamber through ignition outlets formed therein, and into a primary combustion chamber, providing a hotter, more uniform ignition catalyst to a main charge of fuel and air than an igniter could provide alone.
In comparison to other ignition strategies, the reliability and effectiveness of spark-ignition can be more reliant on fuel quality and the uniformity of the air-fuel mixture. For example, fuels such as natural gas may experience ignition problems or unstable combustion, especially in lean mixtures, due to variations in fuel quality. These and other issues may negatively impact ignition and combustion in both the prechamber and the primary combustion chamber, possibly causing issues such as unreliable ignition timing, ignition failure, engine knock, increased exhaust emissions such as NOx, decreased thermal efficiency, and overall reductions in engine performance.
Attempts have been made to combat these and similar issues by adjusting fuel and/or air delivery to the prechamber. One such strategy is set forth in U.S. patent application Ser. No. 15/296,181 to Yeager (“Yeager”), now U.S. Pat. No. 9,903,264. Yeager proposes a control system for an engine cylinder structured to adjust fuel delivery responsive to the relative pressure ratios in a prechamber and a main combustion chamber. The system utilizes pressure sensors positioned in both the prechamber and the main combustion chamber. A processor apparently generates a signal to alter delivery of fuel to the prechamber or the combustion chamber based on a difference in the pressures. Improved or alternative strategies for determining variations in prechamber combustion properties, and making adjustments to various ends remain desirable in some applications.